In a multiwindow system in which a plurality of windows are set on a display screen at positions such that these windows partially overlap and the display priority and position of each window can be arbitrarily changed, when the operator instructs to change the display priority of the window, a check is automatically made to see if there exists the window which will be completely covered by the other windows having priorities higher than that of this window and will fully disappear from the screen if the display priority is changed or not. If such a window is found out, the display priority of this window is changed in the state in which this window is automatically shifted to the position where a part of this window can be seen on the screen, thereafter the window is displayed on the screen. The changing process of the display priority of the window and the automatic shifting process of the position of the window are controlled by referring to and correcting the contents of the window management tables in which the data indicative of the sizes, positions, display priorities, and the like of the respective windows is stored.

An image data display system in which more than one portion of an image displayed on a screen may be transformed by extraction, scaling or rotation in relation to other areas of the screen concurrently. The image display system is of the type which is capable of receiving transformation operation orders from a control processor prior to being sent the image. As the image is received, the display system performs the transform operations prior to displaying the image data. The control processor is modified to include means to determine when two or more concurrent transforms of portions of an image will cause the portions to be displayed on common areas of the display screen (or overlap) and, means to order and transmit to the display device the list of transforms to be performed so that the image pel definition signals are transmitted to the display device where image portions occupy common areas of the display screen the pel definition signals relating to higher priority portion of the image control the final content of the common areas of the displayed image.

An interactive display system includes a display terminal on which an operator may display the data contained in windows (14.1, 14.2 . . . ) on formatted application data (PS 1, PS 2 . . . ) in selected viewports (15.1, 15.2 . . . ) on the screen 13. The system is provided with storage (4), both real and virtual, into which a presentation interface service (2) loads dynamically the entire formatted data (PS 1, PS 2 . . . ) of each application (list 1, list 2 . . . ) as it is invoked by the user. A screen manager (7) maps the data contained in the defined windows into locations (16.1, 16.2 . . . ) of a programmable symbol refresh buffer (6, 8) determined by the corresponding position of viewports (15.1, 15.2 . . . ) on the screen defined by the user and through which the windows are to be viewed.

A computer system including text input and display devices. A display manager receives text from the input device and causes the display device to display that text on a first display level. The display manager also causes other display levels to be displayed so that they are perceived as being successively posteriorly positioned relative to the first level. Text received from the input device is also accumulated and compared to previously stored text segments to cause performance of program task elements that are associated with the stored text segments matching the received text. The display manager causes text produced by the performed task elements to be directed to and perceptually represented on the appropriate posterior display levels.

A data-processing apparatus provided with a bit boundary block transfer unit. A CPU forms a list of parameters required for transferring characters forming one block of text, and stores the list in a memory. A parameter control section of the boundary block transfer unit sequentially reads the parameters, and writes them in a parameter file. Meanwhile, the CPU processes the data. When the block of text has been transferred, an interrupt is supplied to the CPU. The CPU can form a list of only those parameters which must be changed for characters of the same type. These parameters are rewritten as the characters are transferred, one by one. In another data-processing apparatus of the invention, a CPU loads a register with data showing the type of characters to be transferred. It can input a variable parameter to a memory storing fixed parameters. When the variable parameter is set in both the memory and the register, a first selector selects one parameter for one character of the type specified by the data set in the register. This parameter is further selected by a second selector when the register stores said data. When the register does not store said data, the second selector selects the parameter for one character. Any parameter selected by the second selector is set in a parameter file. A data-transferring circuit transfers one character according to the parameter set in the parameter file.